1. Field of the Invention
The present invention relates to a CLV (Constant Linear Velocity) disc applied to optical disc medium, a format of the above-mentioned CLV optical disc, and an optical disc medium recording and reproducing apparatus, in particular, the CLV disc and the CLV disc format in the large capacitance optical disc apparatus capable of recording and reproducing the information on the optical disc medium.
2. Discussion of the Background
In order to raise the speed of accessing the information recorded on the optical disc media, it is necessary to control the speed of moving the optical head precisely and with high speed. When the optical disc apparatus receives the indication of accessing the information from the upper-ranked apparatus, the optical disc apparatus calculates the relationship between the logical number of the information and the physical position as shown by the track number or the sector number on the optical disc, and the apparatus sends the optical head to the above-mentioned physical position.
Hereupon, as to such optical disc, there exist two types of recording method; those are, a CAV (Constant Angular Velocity) type recording method in which the angular velocity is constant and a CLV (Constant Linear Velocity) type recording method in which the linear velocity is constant.
In the CAV type method, since the amount of the information on one track is always constant regardless of the inner and outer circumferences of the disc, the logical information number and the track number (numerical value) can be easily calculatively converted from each other, and thereby the calculation thereof can be done in a very short time. However, according to such CAV type method, there arises a problem that the line density of the information at the outer circumference of the disc is lowered and thereby the entire memorizing capacity is lowered. In order to avoid such unfavorable problem, in a method called xe2x80x9cmodified CAV type methodxe2x80x9d, it is devised that the frequency of the recording signal is raised at the outer circumferential portion of the disc for the purpose of making uniform the line density on the respective inner and outer circumferential portions. However, in such way as mentioned above, there arises another problem that the structure of the formatter electric circuit becomes complicated.
From the viewpoint of the memorizing capacity and the simplification of the formatter electric circuit, the CLV type method is more preferable than the CAV type method. However, in the CLV type method, the amount of the information on one track differs in accordance with the radius position on the disc, and the calculative conversion between the information number and the physical position may become further complicated. As a result, the calculation of conversion therebetween cannot be done in a short time, and thereby, the access time may be elongated. Those matters are the problems of the CLV type method to be solved.
In recent years, as large-capacity optical disc media, DVD-ROM, DVD-R, and DVD-RAM, etc. have become popular, the requirement of increasing the memory capacity of these media continues to grow. Namely, it is desirable that the pitch be narrowed more and more and that the bit is made smaller. In such a situation, providing high-speed access to such an increased large-capacity media has become an important problem to be solved.
In order to solve the above mentioned problem, the published specification of Japanese Laid-Open Patent Publication No. 9-16980 filed by Nihon-Denki Co., Ltd. entitled, xe2x80x9cA METHOD OF ACCESSING THE INFORMATION OF THE CLV OPTICAL DISCxe2x80x9d has already described the method composed of the steps of: firstly determining only the moving direction of the optical head; driving, in advance, the optical head moving medium; obtaining, thereafter, the present position (track number) corresponding to the present address and the target position (track number) corresponding to the access target address by the calculation; calculating the track number therebetween (between the present position and the target position); and finally performing the access control.
However, there is a limitation in the realization of the high-speed operation obtained in such way as mentioned heretofore. Therefore, sufficient high-speed access cannot always be realized.
On the other hand, the published specification of Japanese Laid-upon Patent Publication No. 8-279129 filed by SONY Co., Ltd. entitled, xe2x80x9cA METHOD OF MANUFACTURING THE CLV DISCxe2x80x9d does not describe technology relating to the method of providing the usual CLV format. Instead, it describes the technology relating to a method of arranging sectors without causing any angular positional error obtained at the time of ideally driving with CLV. The above specification has already described the method composed of the steps of: causing the formatter to receive the start position of the start sector""s address from the cutting machine with the same angular information; previously estimating the address situated at the same neighboring angular position as that of the start address by the calculation; changing the buffer length when the sector arrives at the above-mentioned estimated address; confirming thereby the arrival of the electric signal of the angular information sent from the cutting machine; sending the address signal of the next sector and thereby absorbing the variation of the angular position due to the error of the cutting start radius position and due to the change of the track pitch; and making uniform the sector angle between the different stampers.
However, according to the method as mentioned above, it is inevitably necessary to provide special processing such as the estimation of the sector arriving at the same neighboring angular position as that of the start sector and the compensation of the buffer length, etc.
As mentioned above, the background-art CLV optical disc requires a lot of time for performing the calculative conversion between the logical information number and the physical position. Therefore, the speed of accessing the disc information is inevitably lowered. This is a problem to be solved.
To provide a large capacity optical disc medium, it may be profitable to adopt the CLV (Constant Linear Velocity; Line Speed-Constant) format in which the line density of the information becomes constant. However, in the CLV format, in the case of accessing a specified sector, it is required to perform the control operation such that the revolution rate of the spindle motor for rotating the disc is changed in accordance with the disc radius position on which the sector exists and the scanning line speed of the reproducing track is made constant.
On the other hand, while the CAV (Constant Angular Velocity; Angular Velocity-Constant) format is inferior in terms of storage capacity, it is superior as to case of accessing. Namely, the respective sectors are arranged on the radius line of the disc, and all of the sectors can be accessed using the same disc revolution rate at the time of reproducing.
Furthermore, there exists an MCAV format taking advantage of the large capacity of the CLV format and the high-speed accessing of the CAV format. In the MCAV format, plural zones are provided in the radius direction of the disc, one circle of the track is divided into plural pieces of the sector in each of the respective zones, and the number of the divided sectors is increased toward the outer circumferential zone of the disc, and then the distribution of the information amount in the radius direction of the disc is approximated (brought close) to the information distribution of the CLV format and the respective sectors are aligned in the radius direction per each of the respective zones. In such format, regarding the movement between the zones, although it is necessary to change the revolution rate of the disc or to change the frequency of the clock for recording/reproducing under the condition of making constant the revolution rate, the high-speed accessing of the CAV format can be obtained in the respective zones.
The method of accessing disc tracks of discs having these formats is discussed below. At first, as shown in FIG. 11A, regarding the CLV format, the revolution rate of the disc is controlled such that the line speed of scanning the track becomes equal to a predetermined value for the track on the radius position of the specified disc or for the track on the radius position where the pickup is situated now, by use of the period of a specified reproducing data signal or the wobble signal obtained from the zigzag movement of the constant period previously assembled (established) on the track at the time of making the master board.
At the step of controlling the disc revolution number, the address information is decoded and thereby the present address value can be obtained. Next, the seeking operation is started from the difference between the present address and the target address. In the CLV format, the arrangement of the respective addresses is different from each other for the respective discs generally due to the difference of the line speed settings at the time of making the master board or due to the slight (very small) line speed error, etc. in spite of intending to perform the same settings.
Consequently, the seeking operation is performed as follows: Assuming the designated place of the target address, when the pickup is moved it counts the number of the transverse tracks. At the time when the pickup arrives at the assumed track, the address value is acquired again and the difference between the acquired address value and the target address value, if any, is determined. When the former differs from the latter, the position of the target address is assumed again, and the abovementioned operation is repeated until the acquired address arrives at the target address. At this time, the disc revolution rate is always controlled corresponding to the reproducing address position.
Next, the CAV format is described. As shown in FIG. 11B, the revolution rate of the disc is set to a predetermined revolution rate. At this time, the address information of the optional track can be obtained. The address value is obtained, and then the seeking operation is performed from the difference between the obtained address and the target address. In the CAV format, since the arrangement of the respective sectors is definite, it turns out to be possible to arrive at the target address precisely and with high speed by just counting each transverse track number at the time of performing the seeking operation.
On this occasion, it is not necessary to control the revolution rate of the disc as in the case of the CLV format. However, even in this case, it is necessary to set the predetermined revolution rate and to acquire the address value when the present address value is obtained, as in the case of the CLV format.
In the MCAV format, as shown in FIG. 11C, the arrangement of the sector having the respective address is clearly defined. Therefore, the seeking operation to the target address can be precisely done with high speed as in the case of the CAV format. However, in the seeking operation of striding (stepping over) the zones, it turns out to be necessary to control the disc revolution rate of the disk or to control the frequency of the recording/reproducing clock. Even on this occasion, regarding the acquisition of the present address value which is the first operation of seeking, it turns out to be necessary to set the revolution rate to a predetermined revolution rate.
For instance, the published specification of Japanese Laid-open Patent Publication No. 6-231469 discloses the featured address ID data modulated with BPM (Bit Position Modulation) by way of the PE (Phase Encoding) as a background art and recorded on the recording medium. The art does not require any special sector mark and realizes the preferable sector synchronization, and enables to calculate the line speed information of the track from the interval between the detection pulses of the address part. The above-mentioned operation itself is performed on the basis of the disc rotation control corresponding to the position in the radius direction of the disc and the reproduced address value. And then, since there scarcely exists the correlation between the address ID data and the data modulated and recorded with PWM (Pulse Width Modulation), the sector synchronization and the detection of the address ID can be preferably performed in synchronism with each other. In addition, the basis speed of the track can be presumed (assumed) on the lines of the pulse width given (created) by the phase encoding (PE), and thereby the high-speed accessing can be realized.
Furthermore, the specification of Japanese Patent No. 2,689,980 relates to the seeking control in the CLV disc format and discloses the method of the seeking control, in which the wobbling signal of the predetermined frequency is modulated with the address information coded by a frequency lower than the predetermined frequency and the address information is extracted from the wobbling track of the optical disc which is wobbled and thereby formed corresponding to the modulated signal, and in such way the seeking operation is controlled.
Furthermore, the published specification of Japanese Laid-open Patent publication No. 5-266497 discloses the method of the seeking control in the CLV disc format, in which the offset value for the short-distance access and the offset value for the long-distance access are previously programmed, the offset value is selectively used in accordance with the distance to the place to be accessed, and then the track jumping is performed. In such seeking method, the accessing operation can be intended to speed up.
Furthermore, according to the method of accessing the information of the CLV optical disc discloses in the published specification of Japanese Laid-open Patent publication No. 9-16980, the number of the tracks for moving is calculated from the difference between the present track number and the target track number, the track jumping or seeking operation is performed. However, in such background-art method, there arises a problem to be solved that the accessing operation may be delayed, because the calculation of the logical information number and the physical track position takes a long time, regarding the information accessing of the disc recorded by the CLV method. In the above-mentioned background art, only the moving direction of the optical head is firstly determined, the optical head conveying medium is driven in advance, the present position (track number) corresponding to the present address and the target position (track number) corresponding to the target position (track number) corresponding to the accessing target address are obtained by the calculation, and the number of the tracks therebetween is calculated and thereby the control of accessing can be performed.
With the development of the Laser technology, the optical disc medium has been widely used as the recording/reproducing medium and satisfied the demand of large memorizing capacity as DVD-ROM, DVD-RAM, and DVD-R, etc. In order to realize a large memorizing capacity, narrow pitch and small pit are always successively required for those optical disc media.
As to the large memorizing capacity, the CLV disc format capable of realizing the constant line density of the information recording may be profitable. However, in such CLV disc format, when the intended sector is accessed, it is necessary to control the scanning line speed of the reproducing track so as to make it constant by changing the revolution rate of the rotating motor corresponding to the radius direction of the optical disc medium in which the sector exists. As the result, the control of the optical disc medium may become further complicated.
On the other hand, the CAV disc format is profitable in that the respective sectors are arranged on the radius line of the optical disc medium, the accessing with the same revolution rate can be done for every sector at the time of reproducing, the revolution rate of the optical disc medium is set to the predetermined revolution rate, the address value of the optional track is taken in, the seeking operation is done on the basis of the difference between the address value thus taken in and the target address value, the number of tracks traversed is counted, and in such way the operation of accessing the target address can be done effectively.
However, in the above-mentioned CAV disc format, the memorizing capacity per one track is determined by the number of the recordable marks in the recording area of the optical disc medium, and therefore the problem of the large memorizing capacity has arisen.
Furthermore, an M-CAV (Modified CLV) disc format has been also used. The M-CAV takes in the large memorizing capacity of the CLV disc format and the high-speed accessing of the CAV disc format.
In such M-CAV disc format, plural zones are provided in the radius direction of the optical disc medium, the entire circumference of the track is divided into plural sectors in the respective zones, the number of the divided sectors is gradually increased toward the outside zone in the radius direction, and the recording distribution of the information amount in the radius direction of the optical disc medium is approximated to that of the CLV disc format.
Furthermore, in such M-CAV disc format, the respective sectors are arranged in the radius direction per each of the respective zones, the recording frequency is set so as to gradually increase it, and therefore the high-speed accessing of the CAV format can be obtained in the zone.
The background arts in connection with the CLV drive controlling method of the spindle motor and the slide motor and the CLV format in the optical disc cutting machine are described hereinafter.
The published specification of Japanese Laid-open Patent Publication No. 6-36272 relating to the rotation of the disc (corresponding to Japanese Published Patent Publication No. 6-36272) discloses the control operation, in which one time period of the rotation pulse obtained from the rotation pulse generator mounted on the spindle is counted with the constant value by the pulse train obtained from the radius signal generating unit for obtaining the radius signal having the value corresponding to the radius position where the optical pickup exists and the variable frequency generating unit capable of modulating the frequency so as to make constant the product of the radius signal and the frequency, the error of the calculated value is fed back to the speed, and thereby the line speed of the optical disc on the optical track.
The published specification of Japanese Laid-open Patent Publication No. 8-235769 relating to the method of controlling the motor revolution rate and the apparatus for practicing the above controlling method discloses the method of obtaining the revolutions rate variation further approximated to the revolution rate variation in the ideal CLV method by the following two methods:
(1) A motor rotation controlling method of controlling the motor rotation by stepwisely reducing the variation rate of changing the number of revolutions of the motor corresponding to the positional variation of the optical disc in the radius direction; and
(2) A motor rotation controlling method of successively and alternately providing the first section (block) in which the motor rotation is controlled by stepwisely reducing the variation rate of changing the number of revolutions of the motor corresponding to the positional variation of the optical disc in the radius direction and the second section (block) in which the motor is rotated with a constant number of revolutions and controlling the rotation of the motor in such first and second sections as mentioned above.
The specification of Japanese Patent No. 2,844,565 relating to the CLV controlling apparatus discloses the method of controlling the revolution rate of the spindle on the basis of the target line speed data and the radius position data.
The published specification of Japanese Laid-open Patent Publication No. 8-279192 describes the method of manufacturing the CLV disc. The Laid-open Patent does not directly relate to the CLV controlling method. Instead, it relates to the arrangement of the sectors without any angular position error which can be obtained in the case of performing the ideal CLV drive at the time of cutting the CLV disc format.
The formatter receives the start position of the start sector address with the same angle information from the cutting machine. The address coming close to the same angle as that of the start address is previously estimated by the calculation. When the sector comes at the above address, the buffer length is changed, and then the arrival of the electric signal of the angle information sent (transmitted) from the cutting machine is confirmed, and then the address signal of the next sector is sent out. In such way, the error of the cutting start radium position and the variation of the angular position due to the track pitch variation can be absorbed. Thereby, the sector angles between the different stumpers can be aligned (made uniform).
Regarding the method of evaluating the CLV drive accuracy of the spindle motor or the slider in the optical disc master board exposing apparatus, the method of controlling the CLV drive, and the apparatus for practicing those methods, it is noticed that the phase difference of the pulse train having the constant period length between the adjacent tracks due to the fundamental clock linearly changes.
Heretofore, the background arts regarding the CAV optical disc and the CLV optical disc and the CAV and CLV type methods of disc formatting etc. have been described. However, according to such background arts which are disclosed in background-art documents, e.g., Japanese Laid-open Patent Publication Nos. 9-16980 and 8-279192, there exists no advantageous functional effect for improving the CLV optical disc and the CLV type method of disc formatting. The present invention has been made in view of the above-mentioned problems and other problems in order to solve the unfavorable problems.
To state in more detail, the present invention solves the background-art defects such as the above-mentioned problems. The present invention provides an improved CLV optical disc and the CLV type method of disc formatting. The present invention solves the problems of the background art that the calculative conversion of the logical information number and the physical position from each other require a lot of time to perform and adversely affect the speed of accessing the disc information.
In consideration of such problems (defects) of the background art, the present invention enables to realize the CLV optical disc capable of facilitating the calculative conversion of the information number and the track number from each other, eliminating the unevenness of the format of the disc manufactured by use of the different optical disc master board (plate), and accessing the disc information with high speed. Other objects, features and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.
In the background arts, the first part of the seeking operation is performed on the basis of the control of the disc rotation corresponding to the position in the radius direction of the disc and the reproduction of the address information previously recorded as the wobbling track. However, the respective information amounts on the optical disc differ from each other. As the result, the conversion from the information number and the number of tracks, and vice versa, may become difficult. In accordance with the tendency to increase memory capacity, the track pitch is narrowed and the information pit is small-sized. Consequently, the conversion between the information number and the tracks number may become further difficult.
The present invention was made in order to solve such problems. The invention realizes the complete disc format and provides the CLV disc format capable of accessing the optional address with high speed.
As to the optical disc medium recording and reproducing apparatus, the CLV (disc format) is profitable for the optical disc medium. The primary condition required in the multiple-media era is the large memorizing capacity with the high recording density capable of recording and reproducing the image of high quality and the audio signal of high sound quality. Regarding this point, the CLV and the M-CLV satisfy the demand. Forming the sector of constant length, the data can be recorded in synchronism with the constant clock. The condition of recording and reproducing the laser power, etc. on every position of the optical disc medium.
In such CLV disc format, the revolution rate of the optical disc medium is controlled corresponding to the position in the radius direction so as to make the track scanning line speed equal to the predetermined value by the period of the specified reproducing data signal or the wobble signal of a constant signal previously assembled in the track at the time of making the master board, for the track on the predetermined radius direction of the optical disc medium or the track on the radius direction where the pickup is located. In such state, the seeking operation is performed.
Generally, in the CLV disc format, since the arrangement of the respective sector slightly differs from each other per each of the respective master boards due to the setting error at the time of setting the line speed when the master board is made, the target address is set at the time of the seeking operation, and counting the number of tracks traversed as the pickup is moved. When the pickup arrives at the setting track, the address value is taken out again. Such taking-out of the address value is repeated until the address value arrives at the target address value. In such way, in the CLV disc format, it is necessary to perform the seeking operation after controlling the revolution rate of the optical disc, and the seeking operation cannot be performed with high speed. Those are the background-art problems to be solved.
The present invention was made in consideration of the present state of the seeking operation performed by the optical disc medium recording/reproducing apparatus. The invention aims at providing the CLV optical disc medium recording/reproducing apparatus capable of performing the seeking operation independently from the operation of controlling the revolution rate of the disc.
In the recent years, DVD-ROM, DVD-R, and DVD-RAM, etc. have become popular. In the DVD standard specification, it has been required that the fine-structure preformat of almost half size should be formed on the optical disc master board, compared with the first case of track pitch: 0.7 xcexcm and the minimum pit length: 0.44 xcexcm and the second case of the present standard specification of track pitch: 1.6 xcexcm and the minimum pit length: 0.87 xcexcm. In accordance with the demand of increasing storage or memory capacity, further narrowed track pitch and even smaller sized pits are inevitably required. And, in addition, it is further required to provide the optical disc cutting machine of high accuracy and high quality.
Under the aforementioned circumstance, when the disc of the CLV format is cut, the CLV drive control with further high accuracy is required in the optical disc cutting machine. Further, the line speed of cutting the disc is required to be constant regardless of the radius cutting position. Therefore, the revolution rate of the spindle and the moving speed of the slider have to be controlled such that both of them continuously (successively) reduce in inverse proportion to the radius position variation.
The period of the pulse train obtained by the rotation pulse generator mounted on the spindle by use of the pulse train obtained from the variable frequency generator in which the output frequency is changed in inverse proportion to the radius position. Thereby, the CLV drive control can be realized. In such method, the standardized pulse train for the CLV drive can be created by the medium (potentiometer) for detecting the radius position and the variable frequency generating medium. The detection error of the radius position and the setting error of generated frequency are included therein. In such way as mentioned above, even though the accuracy required in the background-art CLV drive control can be attained, those errors cannot be ignored and have to be removed in order to realize the further high-accuracy CLV drive control.
Furthermore, the general rotation pulse generator is constructed such that the circular disc board having slits radially formed thereon is mounted on the spindle shaft, the light source and the light detector are arranged so as to put the slit therebetween, and the rotation pulse can be obtained by directing the light as the incident light accompanying the rotation of the spindle and intercepting the same light. At this time, even though the slits are precisely and radially arranged so as to divide them at an equal interval, it is observed that the seeking speed variation is included in the rotation pulse train due to the mounting eccentricity of the slit circular disc board onto the spindle shaft. In case that the rotation pulse train is employed as it is for the feedback of the rotation drive, the efficiency of the control is lowered contrary to the expectation. Even in the optical disc cutting machine, the CLV drive control is performed with the almost similar construction. In order to improve the CLV drive accuracy, the reading-out accuracy is firstly intended to improve, and then the pitch accuracy is mainly intended to also improve.
In the background art, the revolution rate is changed with a constant changing rate for the position in the radius direction, or otherwise, the relationship between the radius position and the revolution rate is approximated further close to the ideal relationship therebetween by alternately providing a section in which the revolution rate changes with a constant changing rate and another section in which the revolution rate is constant, in order to make the actual revolution rate fall within the predetermined error area (range) for the ideal revolution rate change of the spindle corresponding to the position in the radius direction. Even in such method, as to the revolution rate of the CLV drive, a revolution number pattern, etc. of a certain designated constant is generated and changed over from those values on the radius position as the standard. In order to further raise the CLV revolution (rate) accuracy, it is necessary to intend to raise the accuracy of the linear scale for detecting the radius position and also intend to raise the number of the multiple changing-over points.
In the other background art, although the art does not relate to the direct CLV drive control, if the ideal CLV drive is always performed, the positional relationship of the respective sectors on the CLV disc which is cut by the cutting machine can be always equal. The art aims at realizing such arrangement. Here, previously assuming (estimating) the sector coming to the position near the same angle as that of the start sector, when the sector arrives at the position, the deviation from the estimated value is compensated (corrected) by changing the buffer length. In such way, the positional relationship between the respective sectors is made almost equal and thereby the cutting can be enabled. However, it is necessary to provide the special processes such as the estimation of the sector coming to the position of the same angle as that of the start sector and the compensation of the buffer length.
FIG. 21 illustrates a fundamental structure of the background-art optical disc cutting machine. The reference numeral 201 represents an exposing laser for exposing a glass master board 205 having a photoresist painted thereon (applied thereto). The reference numeral 202 represents an optical system for shaping the waveform of the exposing laser light emitted from the exposing laser and guiding the exposing light to a focus actuator 204. In such optical system, the focus actuator 204 insures that the exposing laser light directed as the incident light is focused in the state of a microspot. The focusing control is performed so as to keep the beam waist position to the photoresist position. The optical system, etc. for performing the focus control is omitted here. An optical modulator 203 turns on and off the exposing laser light on the basis of the signal Fout transmitted from the formatter 215 for causing to generate the signal for forming the pre-embospit or the groove on the glass master board 205. The reference numeral 216 represents a fundamental clock generator for generating the fundamental clock in order to drive the formatter 215. The glass master board 205 is absorbed (attracted) to the spindle motor 206 and rotated thereby. At the same time, the focus actuator 204 is moved in the radius direction by the action of the air slider 208. An encoder represented by the reference numeral 207 is mounted on the spindle motor and outputs a pulse train in accordance with the rotation. The reference numeral 214 represents a linear scale for detecting the radius position of the exposure spot. The reference numerals 209 and 211 represent drivers for respectively driving the slider and the spindle. The reference numerals 210 and 212 represent control circuits for respectively causing the slider and the spindle to follow thereto smoothly and with high accuracy for the movement order and the rotation order both indicated by a drive-system controller 213. The sensor for detecting the absolute position in order to preset the value of the linear scale is omitted here. Furthermore, although the two-beam exposure, and the zigzag movement of the exposure beam, etc. of the optical disc cutting machine are required to be set corresponding to the various sorts of disc format, the various sorts of the exposure optical system, etc. required therefor is omitted here because it does not directly relate to the present invention. By use of the aforementioned structure, the CLV drive is performed as follows:
At first, the drive-system controller 213 reads out the radius position (xcex3) of the present exposure spot from the linear scale 214. Next, the rotation ordering pulse of the spindle motor 206 is generated by use of a spindle drive ordering pulse creating circuit 217 so as to satisfy the following equation:
V1=xcex3.xcfx89=(constant),
In accordance with the designation of the exposure line speed (V1), and then the revolution rate of the spindle motor 206 is controlled to the value w.
As to the CLV drive of the slider, in the similar way, the slider drive ordering pulse is generated from the value r by use of a slider drive ordering pulse creating circuit 218 so as to satisfy the following equation:
V1=Vsxc3x97rxc3x972xc3x97xcfx80/P=(constant).
Here, P is the spiral pitch. In such way, the moving speed is controlled to be Vs. Or otherwise, there exists another way of performing the control of moving the slider only by the spiral pitch during one revolution of the spindle.
In such a CLV drive method, the error or the variation of the radius position information of the exposing spot directly exerts an influence upon the rotation control of the spindle. Consequently, the arrangement of the respective sectors of the CLV format cannot be precisely controlled.
In order to solve the problems mentioned above, the present invention provides a method of creating an ideal CLV drive ordering pulse creating method for the spindle and the linear motor in the optical disc master board exposing apparatus.
The present invention provides a further local CLV drive ordering pulse creating method with small deviation and high accuracy. The invention further provides the CLV disc format enabling to create the high-accuracy CLV drive ordering pulse approximated further close to the ideal, without producing the accumulated error accompanying the operational calculation error per each of the respective tracks. The present invention further provides the CLV disc format enabling to create the high accuracy CLV drive ordering pulse with small local deviation in the track and with high accuracy further close to the ideal.
The present invention further provides the CLV disc format capable of creating the pulse train without any error for the railroad track length increase xe2x80x9cxcfx80xc3x97Pxe2x80x9d of the one track after starting the CLV drive.
The present invention further provides the CLV disc format capable of creating the pulse train without any error for the railroad track length increase xe2x80x9cxcex8c2/(4xc3x97xcfx80)xe2x80x9d of the one segment after starting the CLV drive.
The present invention further provides the CLV disc format capable of creating the pulse train without any error for the fundamental railroad track length xe2x80x9c2xc3x97xcfx80xc3x97R0xe2x80x9d at the time of starting the CLV drive.
The present invention further provides the CLV disc format capable of creating the pulse train without any error for the fundamental railroad track length xe2x80x9cxcex8cxc3x97R0xe2x80x9d at the time of starting the CLV drive.
The present invention provides a method of controlling the CLV disc format exposure drive without any accumulative error for the ideal CLV drive. The present invention further provides the method of controlling the CLV disc format exposure drive such that the absolute position on the disc per access unit of the respective sectors formed on the CLV format disc or the relative positional relationship between the access unit (the positional relationship of the track and the angular relationship in the circular circumferential direction) is made equal to the arrangement on the ideal CLV disc format, and the access operation can be enabled, in which the ideal CLV disc format is assumed in the movement of the pickup to the address unit designated by the drive apparatus.
As is further apparent from the foregoing description, according to the present invention, the advantageous functional effects can be further realized as mentioned below.
In an aspect of the present invention, the drive of the spindle motor and that of the slider are controlled by use of the spindle rotation ordering pulse train and the slider movement ordering pulse train respectively created by frequency-dividing the fundamental clock pulse train, the respective frequencies of which are proportional to the ideal railroad track length which can be determined by the starting radius position of the spiral, the number of the tracks, and the spiral track pitch, per one revolution of the spindle.
In such structure, since the drive ordering pulse is created in synchronism with the fundamental clock of the CLV format per each one revolution of the spindle, it is possible to obtain the drive ordering pulse train having a very small accumulative error due to the ideal drive ordering pulse variation.
Furthermore, in the CLV drive control according to the present invention, only the data of the drive starting position and the radius position data are required. The other subsequent radius position data is not required. Consequently, a linear scale of high precision for detecting the radius position is not required. As a result, the cost of the entire apparatus can be reduced.
In another aspect of the present invention, the drive of the spindle motor and that of the slider are respectively controlled by the spindle rotation ordering pulse train and the slider movement ordering pulse train generated by frequency-dividing the fundamental clock pulse train in proportion to the number of the ideal railroad track length determined by an equal rotation angle or an optional rotation angle xcex8c in a segment identified with a line segment on the spiral track divided by the equal rotation angle or the optional rotation angle xcex8c, per one revolution of the spindle, the start radius position of the spiral, the number of the spiral segments, and the track pitch of the spiral, per each one revolution of the spindle.
In such structure, since the drive ordering pulse can be created in synchronism with the fundamental clock of the CLV format per each segment, it is possible to obtain the drive ordering pulse train with a very small accumulative error due to the ideal drive ordering pulse variation and having very small local error.
In still another aspect of the present invention, when Ro is the CLV format start radius and P is the spiral track pitch the physical fundamental length is established such that the railroad track length 2xc3x97xcfx80xc3x97Ro+xcfx80xc3x97P at a first track during one revolution of the spindle is an integral multiple of the fundamental clock or finite figure times being realizable at time of the operation calculation.
At a second track and all subsequent tracks, the physical fundamental length is established such that the increasing railroad track length 2xc3x97xcfx80xc3x97P during one revolution of the spindle is an integral multiple of the fundamental clock or finite figure times being realizable at the time of the operational calculation.
Furthermore, in still another of the present invention, when Ro is the CLV format start radius and P is the spiral track pitch, the physical fundamental length is established such that the railroad track length xcex8cRo+Pxc3x97xcex8c2/(4xc3x97xcfx80) at a first spiral segment during one revolution of the spindle is an integral of the spiral segment identified with the line segment on the spiral railroad track created by dividing the one revolution of the spindle by an equal rotational angle or an optional rotation angle xcex8c.
In such structure, it is possible to obtain the drive ordering pulse train having almost no accumulative error due to the ideal drive ordering pulse variation.
In still another aspect of the present invention, the recording medium of the CLV disc format obtained by use of the exposing drive control of the CLV disc format can perform the accessing operation utilizing the positional relationship, because of the coincidence of the arrangement on the disc in the circular circumference per each of the respective accessing units and the number of the tracks with the ideal CLV disc format.